1. Field of the Invention
The present invention relates to a microwave module having a converter for improving transmission characteristics in a millimeter-wave band, and more particularly, to a microwave module having a converter capable of, when a microstrip transmission line and a conductor-backed coplanar waveguide (CBCPW) transmission line are connected by wire bonding, reducing a change in impedance caused by bonding wires and an abrupt change in electric field components between the two transmission lines to thereby improve transmission characteristics in a millimeter-wave band.
This work was supported by the IT R&D program of Ministry of Information and Communication/Institute for Information Technology Advancement [2005-S-039-02, SoP (System on Pakage) for 60 GHz Pico cell Communication.]
2. Discussion of Related Art
Frequencies in the millimeter-wave band, which are radio frequency resources above 30 GHz, are being actively examined as frequency resources for the next generation information communication service. The frequencies in the frequency band can transmit a large amount of information at high speed using a wide-band characteristic. In addition, since the frequencies are highly attenuated in air, the same frequency band can be used in adjacent areas without interference. Therefore, the frequencies have been a matter of concern for many researchers. Currently, development of an information communication service and system using a millimeter-wave frequency is underway, together with research and development of varieties of device parts required for the above-mentioned information communication service and system. Also, research on implementation of a system in the form of a system on package (SOP) using a packaging method of the millimeter-wave band is vigorously progressing.
As the most suitable technology for an SOP method, low temperature cofired ceramics (LTCC) or liquid crystal polymer (LCP) technology is considered. When an active device, such as an amplifier, etc., is installed on a package substrate using such LTCC or LCP technology, flip-chip bonding and wire-bonding are used as a method of interconnecting a transmission line with an active device on the substrate.
The flip-chip bonding demands a very short interconnection and thus can reduce the influence of inductance due to bonding. In addition, when there are a large number of bondings, the flip-chip bonding facilitates bonding operations. However, in the millimeter-wave band, particularly in an extremely high frequency (EHF) band above 60 GHz, transmission loss abruptly increases.
The wire-bonding forms a simple structure and does not need complex equipment, and thus is widely used. However, since the influence of inductance increases with frequency increase, matching is difficult. In addition, insertion loss and return loss increase at a high frequency as in the millimeter-wave band.